Reliability-first, emissions reduction in grid-connected PV-coal systems: Optimal PV integration and coal dispatch under emission caps

Coal-dependent power systems must reduce cost volatility and emissions while maintaining reliable supply under rising demand. This study assesses whether a practical transition architecture, high-penetration photovoltaic (PV) generation combined with a dispatchable coal unit and grid support, can improve techno-economic and environmental performance without sacrificing feasibility. A grid-connected PV-coal-grid hybrid system was modelled and optimized in HOMER Pro, and a sensitivity campaign was conducted by varying coal fuel price, global horizontal irradiance (GHI), and load demand to test robustness and dispatch shifts. The least-cost feasible solution within the explored design space comprises 145 MW PV and a 75 MW coal power plant with grid interaction. Under baseline conditions, the optimized system achieves a net present cost (NPC) of $632 million and a levelized cost of electricity (COE) of $0.049/kWh. Sensitivity results show that increased GHI consistently reduces NPC and COE, while coal price increases drive greater PV utilization in dispatch without undermining feasibility. Load growth increases total system cost due to higher capital and operating requirements, yet COE changes remain modest, indicating improved utilization of installed assets at higher demand levels. The optimized configuration’s emissions inventory quantifies the residual environmental footprint of the least-cost reliable solution, including 429.2 million kg/yr CO₂, 3.30 million kg/yr SO₂, 0.44 million kg/yr NOₓ, 2.30 million kg/yr CO, 19.7 thousand kg/yr particulate matter, and 122 thousand kg/yr unburned hydrocarbons, reflecting reduced coal combustion through PV displacement during high-resource periods. These findings demonstrate that an optimized PV-coal-grid hybrid can deliver cost-competitive electricity, operational robustness to fuel/resource/demand uncertainty, and measurable multi-pollutant emissions mitigation, offering a realistic transition pathway for coal-reliant systems.